[PATCH 3.13.y-ckt 088/121] nfs: Don't busy-wait on SIGKILL in __nfs_iocounter_wait

From: Kamal Mostafa
Date: Tue Dec 02 2014 - 14:23:11 EST

3.13.11-ckt12 -stable review patch. If anyone has any objections, please let me know.


From: David Jeffery <djeffery@xxxxxxxxxx>

commit 92a56555bd576c61b27a5cab9f38a33a1e9a1df5 upstream.

If a SIGKILL is sent to a task waiting in __nfs_iocounter_wait,
it will busy-wait or soft lockup in its while loop.
nfs_wait_bit_killable won't sleep, and the loop won't exit on
the error return.

Stop the busy-wait by breaking out of the loop when
nfs_wait_bit_killable returns an error.

Signed-off-by: David Jeffery <djeffery@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
[ kamal: backport to 3.13-stable: context ]
Cc: Moritz MÃhlenhoff <muehlenhoff@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
fs/nfs/pagelist.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 2ffebf2..27d7f27 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -113,7 +113,7 @@ __nfs_iocounter_wait(struct nfs_io_counter *c)
if (atomic_read(&c->io_count) == 0)
ret = nfs_wait_bit_killable(&c->flags);
- } while (atomic_read(&c->io_count) != 0);
+ } while (atomic_read(&c->io_count) != 0 && !ret);
finish_wait(wq, &q.wait);
return ret;

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